The technology is in its early stages, there's no proven business model and there's strong disagreement about how the trend will play out. But most experts agree that voice over IP (VOIP) will eventually combine with new types of wireless broadband to change how businesses and consumers acquire and use mobile and fixed voice services.
That means you eventually could walk down the street talking over a cellular network, and the call will seamlessly switch to voice over WLAN when you enter your office, which would cut down on the number of cellular minutes you and your company must purchase. Another example: Software in your phone will automatically route your calls over a voice-over-WLAN system when you are inside a warehouse where the cellular signal is weak and switch to the cellular network when you are outside where the WLAN doesn't reach.
Most important, perhaps, is the possibility that this emerging trend -- and the convergence technology behind it -- could create new challengers to cellular and landline operators. That, in turn, could lead to new and more intense competition.
"Cellular operators aren't thrilled about this idea yet," said Derek Kerton, principal of Kerton Group, a telephone market research and consulting firm. "If [subscribers] think they could cut their [cellular] service from, say, 1,000 minutes to 200 minutes, that explains why they're not too excited."
"Everything is starting to blend, and there are no clear lines about who will provide what kind of service," acknowledged Tony Krueck, vice president of product development for U.S. mobile carrier Sprint. "It'll take a while to work itself out."
At the heart of this issue are some brand-spanking-new technologies and some new twists on older technologies that converge high-speed landline and wireless Internet access with VOIP. These technologies enable VOIP, which is already a reality in many homes and offices, to become mobile.
The furthest along of these emerging wide-area wireless technologies are wide-area Wi-Fi mesh networks, which proponents claim can cover entire metropolitan areas. In the U.S., cities such as Philadelphia have received the lion's share of attention about their citywide mesh networking plans, but this technology is already in place in a number of smaller cities.
Some believe that citywide Wi-Fi alone will change the mobile voice landscape, opening the way for increased adoption of mobile VOIP. However, others, such as Phil Redman, a research vice president at Gartner, don't believe Wi-Fi mesh is up to the task.
"One big reason municipal [Wi-Fi] services will fail is that there's no control," Redman said. "This is unlicensed spectrum, so if I blast you with my private networks, there's nothing much you can do about it."
Also, he noted that the current Wi-Fi standard doesn't have built-in quality of service to ensure voice quality, an issue that will be resolved when the next Wi-Fi standard, 802.11n, is ratified later this year or early next.
Interestingly, Wi-Fi's reputed failings aren't discouraging Sprint. Krueck disclosed that his company is working on a consumer-level phone, which internally is called the Combophone, that can handle both voice over Wi-Fi and cellular calls.
"When you enter your home, there will be a special wireless [Wi-Fi] router that would pair with the Combophone," Krueck said. "Once you leave the house again, you'd use the [cellular] network for your calls."
Krueck stressed, however, that Sprint's Combophone won't work over Wi-Fi outside the home -- the planned Sprint router is necessary to make the VOIP part of the system work, and that router will be available only for in-home installation. He said he expects Sprint's Combophone to launch in the first half of next year.
While use of Wi-Fi for VOIP has its detractors, more robust and far-reaching mobile wireless technologies also are emerging. The best known of these technologies is mobile WiMax. Fixed WiMax is already a fully ratified standard, and the mobile version could be approved as soon as the end of this year.
In addition, IPWireless' UMTS TDD and Qualcomm's FLASH-OFDM are already mobile and available. All three of these technologies create wide-area IP-based networks and usually operate in licensed portions of spectrum, which makes them less prone than Wi-Fi to problems such as interference.